In certain automobiles manufactured by various auto companies, the cooling system used for the engine is of the so called "closed" type wherein a plastic degas tank is provided that is physically separated from the radiator and is closed by a pressure cap of a type normally located on the radiator. The degas tank is operated under internal pressure of about 15 PSI gage and is connected to the engine and the radiator so that the coolant circulates through the degas tank. One purpose for the degas tank is to allow entrained air and gasses in the coolant to be separated from the coolant as the coolant flows through the degas tank. In order to allow the air and gasses to escape into the degas tank, it is normal to provide the degas tank with a number of chambers or compartments which are connected in series through windows or openings formed in the ribs separating adjacent chambers so as to allow the coolant to flow between the chambers. During the injection molding process for making a degas tank of this type, the openings are formed in the ribs of the tank by using movable gate members in the molding die. When a gate member is in the closed position, the mold is filled with a liquid plastic material and, after solidification of the plastic material, the gate is moved by lifters laterally out of the opening and the die is retracted with the gate clearing the wall. As should be apparent, providing lifters within the molding die for moving the gates laterally increases the cost of the tooling for forming the degas tank. Not only does it increase the tooling cost, but increased maintenance for tooling of this sort is required.
The present invention solves the above problem by providing a two-part plastic degas tank in which the ribs separating the chambers in each part of the tank are formed with open-ended slots so as to reduce tooling cost by eliminating the multiple lifters heretofore used in the molding dies. The slots are formed in the ribs of each portion of the tank in a manner so when the two parts of the tank are joined together, the slots in opposed ribs register with each other to form an opening through which coolant can flow between the adjacent chambers.
A reservoir tank having certain similarities to the degas tank according to this invention can be seen in U.S. Pat. No. 5,111,776, issued on May 12, 1992 to Matsushiro et al. In FIG. 9 of the Matsushiro et al patent, the partitions of the tank are provided with holes and the Matsushiro specification indicates that slits or grooves in place of the holes can be provided in the walls for communication of the chambers provided in the tank. However, in Matsushiro there is neither a teaching of having a tank formed of two parts as required to practice this invention nor is there any mention of having open-ended slots located in pairs and cooperating with each other for forming an opening within a rib which serves as a partition between chambers.
In addition, Matsushiro et al fails to teach having openings between chambers which extend from the top wall to the bottom wall of a chamber or having enlarges sections formed with the ribs for increasing the bonding areas between the two parts of the degas tank. Both of the latter mentioned differences are added features of the present invention.